Deformation and fracture of hydrogen energy materials

Visualization of hydrogen accumulation in materials during fatigue

Nowadays, it has been studied that the energy source originated from oil is replaced to hydrogen. In order to utilize hydrogen safely, it becomes important to clarify the effect of hydrogen on mechanical properties of industrial metallic materials. Until now, it was considered to be difficult to detect hydrogen accumulation in the metallic materials. Recently, our group has developed the unique method being able to detect hydrogen accumulation by use of the chemical reaction between hydrogen and silver bromides (Hydrogen Microprint Technique, HMT). In HMT, prior to the testing, spherical silver bromide particles having a diameter of 100 nm are distributed on the specimen surface. Then, the site of diffusive hydrogen emission can be visible as the distribution of silver particles. The photo shows the hydrogen distribution in the fatigue deformed aluminum alloy used for hydrogen storage materials. It was clarified that hydrogen was accumulated preferentially at planer slip bands adjacent to the fatigue fracture zone. This is the direct evidence for the transportation of atomic hydrogen by moving dislocations in the aluminum alloy. Our future goal is to correlate internal stress-strain distribution with hydrogen accumulation in the materials, which contribute to establish the guideline of safe material development in the hydrogen environment.